Mass Flow Meters for Gas Sampling

Digital gas mass flow meters make sampling simple

Gas sampling is the first step in the collection of data that guards process variables, monitors emissions and verifies that processes are running consistently.

We notice a growing demand for regular interval sampling that needs to be consistent and reliable. Sample specialists have discovered the simplicity and economics of the Vögtlin red-y compact 2 series mass flow meters with optional integrated alarm module.

Making sample taking simple

In the analytical world the red-y compact 2 meter is used as the heart of a reliable automatic, low cost gas sample taking device. Emission or environment measurements often demand periodic samples of a fixed amount of gas and collect these in a container or sample bag.

For example every hour a 100 scc sample. The red-y compact 2 meter with its optional smart alarm module has the complete solution without the need of any PLC to control the process.

Figure 1: Basic electrical diagram of periodic gas sampling system

The system runs on 24 Vdc and a very simplified diagram can be seen in figure 1. The compact 2 alarm module has 3 alarm points that are individually programmable for different alarm functions, such as totalizer, window, high and low alarm. We will also make use of the timer functions and the ability to reset the alarms and totalizer with an I/O input on the alarm module.

We program Alarm 1 as a totalizer alarm with the sample volume we want to collect in each sample, in our example 100 scc (Standard cubic centimeter).

In that alarm function we can also program a duration of the alarm between 100 msec and 2.78 hours. This time sets the time between the samples. Once the process starts, the solenoid will open and a pre-set amount of gas will flow into the sample bag or container. One the defined amount is reached, the Alarm 1 will open and close the solenoid, and the gas flow will stop. Because of the programmed Alarm 1 duration setting the alarm will stay active for the pre-programmed time, in our example 1 hour.

Once this hour is over, Alarm 1 is programmed to automatically reset itself, the counter goes back to zero. The solenoid is activated again, the gas will flow and the totalizer start counting again till the pre-programmed value is reached. The process starts all over again. The process will continue and every hour one sample of 100 scc will flow into the sample container.

Alarm 3 is used as a diagnostics. The alarm will sound if:

The sample bag/container gets full

Water enters the sample line

The flow during sampling is too low (blockage of sample line)

The flow is too high (Pressure in process too high)

In this case you have to push the reset button to deactivate the alarm and continue the process. There are many other variations possible. Every system is a bit different, you can find additions like purging, filtering, pressure reduction, gas drying, etc. out in the field. Many of the users of these systems obtain a battery powered high accuracy red-y compact 2 meter to verify if the flow meter in the field is working properly or if it needs calibration or cleaning. The red-y compact 2 has a big internal diameter flow channel, has a low pressure drop, is temperature compensated and measures the mass flow, independent of changes in pressure and temperature.

Flexibility

It is impossible to describe all process in which these type of flow meters are used, but if you see a VA meter for gas and you want to improve a process, talk to the experienced Vögtlin engineers and they will be pleased to help you to find a solution.

Conclusion

Customer around the globe make use of the advantages in the analytical field, in research and development, in light industrial applications, in semiconductor segments and other applications. Very often we hear from the users “The beauty about the Vögtlin Thermal Mass flow instruments is that you install, set and forget them, as they work so reliable.”Vögtlin’s world-wide network of distribution and sales partners will help you selecting the equipment that matches best for your application and specific needs. Local service centers in the USA, China and Europe provide the after-sales support.